Wireless Charging for Electric Vehicles a Reality, Researchers Say

First pilot project scheduled for a campus transit bus in 2012.

The wireless power transfer pads deliver a charge even though there's a gap between the ground and vehicle chassis.
Utah State University Energy Dynamics Laboratory

Come next year, students, faculty and staff at the University of Utah may be riding on what officials are touting as the first electric-powered, fully wireless rechargeable transit bus.

Researchers at Utah State University’s Energy Dynamics Laboratory (EDL) say they have perfected “wireless power transfer technology” featuring charging pads embedded in concrete. Through magnetic fields, enough power is transferred to a vehicle so it can operate over a predetermined course. In this case, it’ll be a two-mile campus bus route.

Hunter Wu, principal investigator and research scientist with the EDL, hopes the project is another move toward a viable form of non-fossil fuel power for vehicles. He explained that over the past year, he and his team have developed a 5 kilowatt system that can transfer power over 10 inches of air gap — any sort of space, including through concrete — at an efficiency rate of 90 percent.

In consumer terms, think of a rechargeable pad that a mobile device sits on to wirelessly recharge. But instead of the device being on the pad itself, it could sit on a shelf 10 inches above the pad and still receive the power. That idea is being applied to vehicles.

For the University of Utah bus demonstration, 50 kilowatts of power and multiple charging pads are needed, as is the ability to transmit the power over a foot of space to reach a bus chassis. So the system is being tweaked to improve the transfer ceiling and include more powerful pads capable of recharging the bus at a rate of approximately five minutes for every 10 minutes of operation.

Wu said while his team’s research has demonstrated that the technology can last for more than 20 years, the goal is to extend it to 50 years, so once the pads are embedded, you don’t have to worry about them.

“It’s the challenge of making things reliable,” Wu said. “Although our lab prototype is reliable every time we turn it on, it’s not really designed as a consumer product. It doesn’t have the nuts and bolts inside to make it long-life.”

Commercial Application

To bring the wireless power transfer technology to the masses, a new startup, WAVE Technologies Inc., spun-off from EDL earlier this year. The company has an exclusive license to commercialize the product, and deploying it at the University of Utah is the first step in that plan.

So why is a technology developed at Utah State being demonstrated at the University of Utah, a rival school? Eric Warren, director of public relations for the Utah State University Research Foundation, explained that the decision was mostly due to maximizing exposure.

Utah State is located in Logan; the University of Utah is in Salt Lake City. Choosing a location for the bus route came down to where the bus would be used heavily and receive the most attention.

James May, vice president of business development and program management for WAVE Technologies, said the University of Utah had a new transit route in mind that would take the bus through the center of campus, which he believed would serve as an effective showcase for the technology.

Previously, University of Utah officials didn’t want a bus route in the area, primarily due to an objection over diesel buses traveling through the heart of campus. There’s much less opposition from deans and students over emissions from a rechargeable bus.

The goal is to market the technology, which includes retrofitted buses and the pads, to transit authorities nationwide.

“Transit agencies are really paying attention to this stuff and … are really interested in technology solutions that enable them to operate no emissions or low emissions vehicles,” May explained. “The problem is they are extremely expensive to do right now. What we are doing is allowing transit agencies to run electric vehicles without that extremely high electric vehicle price tag.”

The project will be financed through a $2.7 million Federal Transit Administration grant. The demonstration is being done in cooperation between WAVE Technologies, the University of Utah and the transit agency in Utah, which applied for the grant.

The first part of the funding won’t be disbursed until February or March 2012, and the university is still in the midst of constructing the actual bus route. So at the earliest the project won’t begin until spring next year.

The pilot has been described as a demonstration, but the University of Utah route is intended to be permanent and is meant as the first commercial-scale implementation of the technology, May said.

WAVE Technologies is also working with an engineering consultant to develop containers for the embedded pads, May added, so the top of the container would be level with the road, reducing the “air gap” between the primary pad and the one on the bus.

In addition, while the company is prepared to do a second pilot project if necessary, the hope is that the University of Utah bus route will be the only example needed before transit agencies start purchasing the technology.

“We have to get them comfortable and familiar enough with the technology that they are willing to essentially order buses and charging pads from us, and we’ll provide the bus service as a turnkey, full-service solution,” May explained.

Practical for Consumers?

Wu said the wireless power transit technology is practical for every transit authority because buses typically travel on a schedule and idle for a set period of time. That downtime is ideal for recharging.

He explained that the idea is to improve on the first-generation technology and leap into the second generation — where electric buses can operate on a route for an hour before needing to be recharged. Ultimately transit authorities could then keep their costs relatively low for the technology.

While running local bus routes on the technology seems feasible, is the technology flexible enough to be used on cars for the general population?

Wu, Warren and May all believed that in time the wireless power technology should translate to passenger car use. Practical issues remain, however, including battery size and the cost to rip up roads and install pads at various locations.

Those alterations to infrastructure would be costly, but Wu said electricity is roughly six times cheaper to travel on per mile compared to gasoline engines. In addition, he revealed that high-level modeling done in various universities showed that wireless power transfer technology is feasible.

Wu explained that if the operating costs of the 220 million passenger vehicles running today are compared with an infrastructure that is focused more on investing in roads, the cost of the technology is very competitive with what Americans currently spend on transportation.

To make wireless power transfer work on city streets for buses and perhaps cars is one thing. But what about for vehicles that travel long distances? Wu said long stretches of highway would need to be embedded with more advanced charging pads.

“There are a lot of things that help the equation … to recoup infrastructure costs and we don’t believe it is directly out of the question that this technology is just so cost prohibitive,” Wu said, referring to expanding wireless power transfer out to passenger vehicles. “It’s definitely not. It’s very cost-competitive in the long term.”